The present invention relates to a terrestrial communication system, facilitating audio, video, data, and any other type of communication within a local geographical area, and with an extremely large number of communication channels being made available simultaneously at a very low cost.
Audio, video, and data communication are rapidly increasing sectors of interest, and existing terrestrial communication circuits, radio communication channels and satellite communication systems are used extensively. Dedicated cable systems are also being used to cover local geographical areas with a large number of TV-channels, and these cable systems may also be used for data transmission purposes.
Digital transmission techniques have been developed, and as a result, digital consumer TV transmissions are now available from satellite transponders, and due to the digital techniques utilized, the number of programs transmitted by each transponder is no longer one program only, since several programs can be transmitted simultaneously by each transponder.
However, with regard to terrestrial transmissions techniques, a suitable system has not yet been developed, but it is hoped that such a dedicated system will be made available within the next few years. This will require development of suitable encoders and decoders, specifically developed for terrestrial digital transmission techniques and frequency bands today used for terrestrial TV transmission purposes. Considerable efforts and large sums of money have been invested in the development of suitable techniques, but so far, these efforts have not been successful.
The present invention is based on the discovery that present satellite transmission techniques also can be used for terrestrial transmission.
As a result, a user having equipment intended for reception of digital satellite signals can also use the very same equipment for reception of terrestrial transmissions. This is achieved by arranging communication equipment of the type used in satellites as Local Terrestrial Satellites (LTS) in a mast or other suitable foundation. Transmission from a LTS is based on one of the conventional standards for digital transmission as today used by conventional orbiting geostationary satellites, e.g., MPEG-2 or MPEG-1 or any other standard suitable for audio, video or data transmission purposes. A preferred standard today is frequency modulated MPEG-2 (also compatible with MPEG-1), but other known or future standards may also be used, and amplitude modulated (AM) transmission techniques can also be used as an alternative to frequency modulated (FM) transmission techniques. Each LTS is transmitting using relatively low output power and with an antenna arrangement preferably having none or little directional effect. As a result, a suitable number of LTS can be arranged to cover a local geographical area, giving the inhabitants access to individual communication channels for data, video (TV), and audio communication. The advantages of such a system will be more fully discussed later.
The terrestrial communication system according to the present invention comprises at least one local terrestrial satellite (LTS), preferably located in a mast or any other supporting structure, each LTS having high frequency communication equipment substantially corresponding to a conventional geostationary satellite for digital transmission of video, audio or data, arranged to transmit in the L Band (1-2 GHz), the S Band (2-4 GHz) or a higher frequency band with a relatively low power output and having a preferably omnidirectional antenna installation for transmission in a substantially horizontal plane.